At the Apple’s World Wide Developers Conference ( WWDC 2015 ) the developers of Apple shows the iOS 9 Features and the related content about the iOS 9. iOS 9 is not officially available right now as it is under testing by developers and not available as OTA ( Over The Air ) update. So for your question about the release date check out more in detail :

Dont worry even without any OTA update you can Install iOS 9 Beta 1 Without UDID Errors , update via iTunes. As it is only for Developers so you may face activation error after installing iOS 9. No problem here I am here for your guidance to Install iOS 9 Beta 1 Without UDID Errors. Follow the steps to Install iOS 9 Beta 1 Without UDID Errors :

You must have iTunes updated to latest version , You have it? Proceed to next step

If you download the iOS 9 from the mentioned above website then you will not face any kind of error while updating or after update.

Pre Cautions Before Updating :

If you are a jailbroken user then will prefer to stay on iOS 8.1.2 because there is not any jailbreak is available for iOS 9 or the iOS 8.3. Moreover as it is a beta version and is under testing there are many bugs in this version. There may be a battery drainage problem or etc. So please note this : Update at your own risk , for educational purposes only